Indeed, I've owned a US Blade and an AHPC Viper - both are superb boats. The Viper is supposedly heavier (I have not officially weighed either) - the extra weight seems to be in the beams, the daggerboards and the rudders. The intention for the Viper is to to have a stiffer platform for waves, chop and heavy air - AUS built and delivered.

Does it pay off?? Time will tell.

Additionally, at its current specs - the Viper meets the F104/5 rule. The market in EU is much greater and to meet 2 classes in design may have been preferable. THIS IS MY OWN ASSUMPTION.